Joining device for joining components on a shaft

ABSTRACT

A joining device for joining components on a shaft, e.g., for joining camshaft components on a camshaft tube, is disclosed. The joining device includes a joining device body composed of a material with a heat expansion coefficient that is lower than 10.0 μm/m° C. The heat expansion coefficient of the joining device is smaller than that of the components and/or the shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Application No. DE 20 2022100 979.1 filed on Feb. 22, 2022, the contents of which are herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a joining device for joining componentson a shaft, in particular for joining camshaft components on a camshafttube.

BACKGROUND

When joining components on a shaft, for example when joining camshaftcomponents on a camshaft tube, a highly precise axial dimension isdesirable, which however does not only depend on a positioning accuracyof the joining axis but in major parts also on temperature fluctuationsof the components to be joined and of the joining device itself or of aholding device of the same. A material of the components to be joined orof the shaft is generally specified by their function later on.

In the case of built camshafts for example, the components to be joinedsuch as for example a drive element, a camshaft tube as well as hubcomponents generally consist of steel. Other components, such as forexample sensor wheels or output elements are often formed out of sintermaterials, as a result of which a precise axial dimension can be setonly with difficulty and thus with high cost or not at all.

The present invention therefore deals with the problem of stating ajoining device by means of which in particular the disadvantages knownfrom the prior art can be overcome.

According to the invention, this problem is solved through the subjectof the independent claim(s). Advantageous embodiments are subject of thedependent claims.

SUMMARY

The present invention is based on the general idea of forming a joiningdevice for joining components on a shaft, for example for joiningcamshaft components on a camshaft tube, out of a material the heatexpansion coefficient α of which is smaller than that of steel (12 μm/m°C.), for example smaller than 10.0 μm/m° C. The lower the heat expansioncoefficient α of the joining device is, the more precisely can thecomponents to be joined be joined with respect to their axial dimensionor with respect to their axial position on the shaft. When for examplemultiple components are simultaneously joined on the shaft using thejoining device according to the invention, for example by means of athermal shrink fit, this can be realised particularly advantageouslyusing the joining device according to the invention since here thedifferent heat input of the individual components to be joined, becauseof a component variance or process fluctuations during the heating, hasalmost no effects on the joining device and thus also on the axialdimensions to be achieved, which is why not only a dimensional variancewith respect to the reference surface, but also a dimensional variancebetween individual components to be joined can be significantly reduced.

A further advantage with a joining device having a very small heatexpansion coefficient is that the components to be joined by the same,almost uninfluenced by temperature fluctuations, remain better in termsof a coaxiality between tube axis and joining axis, which likewiseresults in an improved axial dimension precision.

Because of the significantly increased precision with regard to theaxial dimension that can be achieved, rejects can also be reduced andbecause of this a significant cost reduction, in particular also byomission of an additional process for producing a precise axialdimension, be achieved.

In an advantageous further development of the joining device accordingto the invention, the same is formed out of a silicon nitride ceramic(Si₃N₄) having a heat expansion coefficient α of 2.5 μm/m° C. Assumingthe heat expansion coefficient α of steel with approximately 12.0 μm/m°C., a joining device out of a silicon nitride ceramic can accordinglyhave a heat expansion coefficient of merely 21% of that of steel, as aresult of which a significantly more precise axial positioning of thecomponents to be joined is made possible.

In an alternative embodiment of the joining device according to theinvention, the same is formed out of an iron nickel alloy having a heatexpansion coefficient α of 1.7 μm/m° C. A joining device out of an ironnickel alloy thus has merely 14% of the heat expansion coefficient ofsteel, as a result of which the accuracy in particular with respect to ajoining device out of steel or a silicon nitride ceramic can besignificantly increased even further.

Practically, the joining device is formed for thermally joining thecomponents on the shaft. For this purpose, the joining device cancomprise for example an additional heating device which makes possible afurther heating of the components to be joined during the joiningoperation. Particularly during thermal joining, the joining device withits significantly reduced heat expansion coefficient brings out all itsadvantages.

Further important features and advantages of the invention are obtainedfrom the subclaims, from the drawings and from the associated figuredescription by way of the drawings.

It is to be understood that the features mentioned above and still to beexplained in the following cannot only be used in the respectivecombination stated, but also in other combinations or by themselveswithout leaving the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in thedrawings and are explained in more detail in the following description,wherein same reference numbers relate to same or similar or functionallysame components.

BRIEF DESCRIPTION OF THE DRAWINGS

There it shows, in each case schematically

FIG. 1 a joining device according to the invention while joiningmultiple camshaft components on a camshaft tube,

FIG. 2 a detail representation from FIG. 1 .

DETAILED DESCRIPTION

According to the FIGS. 1 and 2 , a joining device 1 according to theinvention for joining components 2 on a shaft 3, in particular forjoining camshaft components 4 on a camshaft tube 5, comprises a materialhaving a heat expansion coefficient α of <10.0 μm/m° C. Concretely, thismeans that the joining device 1 is formed out of such a material,wherein a heat expansion coefficient α of approximately 12.0 μm/m° C.corresponds to that of steel. This means that the joining device 1 isformed out of a material the heat expansion coefficient α of which issmaller than that of the components 2 or the shaft 3 to be joined.Particularly preferably, the joining device 1 is formed out of a siliconnitride ceramic (Si₃N₄) having a heat expansion coefficient α of 2.5μm/m° C.

In a further advantageous and alternative embodiment of the joiningdevice 1 according to the invention, the same is formed out of an ironnickel alloy having a heat expansion coefficient α of merely 1.7 μm/m°C. This means that such a joining device 1 merely has a ¼ or less than ⅕of the heat expansion of steel, i.e. of the components 2 to be joined onthe shaft 3, as a result of which temperature-induced fluctuations ofthe heat expansion of the joining device 1 can be minimised.

A material of the camshaft components 4 to be joined is generallyspecified, wherein for example a drive element 6, the camshaft tube 5and for example cams 7 are generally made of steel. Other camshaftcomponents 4, such as for example sensor wheels or output elements canbe produced for example out of a sinter material. In order to minimisethe influence of temperature fluctuations of the joining device 1, thesame is now produced out of a material the heat expansion coefficient αof which is significantly lower than the heat expansion coefficient α ofthe component 2 and of the shaft 3 to be joined.

In addition it is true that the greater a distance dimension D between areference surface 8 and the joining device 1 is, the greater is also theeffect that can be achieved with the joining device 1 formed accordingto the invention. Upon a simultaneous joining in the joining device 1 ofmultiple, in particular even distinct camshaft components 4 out of amaterial which has a significantly lower heat expansion coefficient α,it is particularly advantageous since here the different heat input ofthe camshaft components 4, because of the component variance or processfluctuations of the heating, has almost no effect on the joining device1 and thus also on the axial dimensions and therefore not only thedimensional variance of the reference surface 8 but also the dimensionalvariance between the individual camshaft components 4 can be reduced.

When for example the differential dimension D amounts to 70 mm betweenthe joining device 1 and the reference surface 8 of the shaft 3, theexpansion variance of the shaft 3, provided the same is formed out ofsteel and has a heat expansion coefficient α of 12 μm per m and ° C. at+/−10° C. temperature differential is 16.8 μm.

A further advantage also is that the joining device 1 and because ofthis also the camshaft components 4 to be joined to the same, almostuninfluenced by temperature fluctuations, remain better in terms of acoaxiality between tube axis and joining axis, which in turn results inan improved axial dimension precision. Because of this, rejects can alsobe reduced as a result of which a substantial cost reduction through theomission for example of an additional process that would be required forproducing the precise axial dimension can be achieved.

All in all, a significantly improved axial positioning of components 2to be joined on a shaft 3 by means of a thermal joining fit can beachieved with the joining device 1 according to the invention. Thejoining device 1 can also be formed for press-fitting the components 2on the shaft 3, in particular with a longitudinal pressing method.

The temperature-induced expansion variance of the joining device 1 in aportion A (see FIG. 2 ), which extends 30 mm in the axial direction, is7.2 μm at +/−10° C. in the case of steel. With a joining device formedout of a silicon nitride ceramic having a heat expansion coefficient αof 2.5 μm per m and ° C., the expansion variance of the portion Aamounts to 1.5 μm at +/−10° C., while the same, with a joining device 1formed out of an iron nickel alloy having a heat expansion coefficient αof 1.7 μm per m ° C. amounts to merely 1 μm at +/−10° C. temperaturedifferential.

This produces a dimensional variance for +/−10° C. for a joining device1 out of steel of +/−12 μm, for a joining device 1 out of a siliconnitride ceramic of +/−9.9 μm and for a joining device 1 out of an ironnickel alloy of +/−9.4 μm.

These values already show that with same assumed temperature variance of+/−10° C. of the camshaft tube 5 and of the joining device 1, atolerance of +/−10 μm with a joining device 1 out of steel is notattainable even because of the heat expansion alone. However, this wouldbe attainable with a joining device 1 formed out of a silicon nitrideceramic or iron nickel alloy.

1. A joining device for joining components on a shaft, comprising ajoining device body composed of a material with a heat expansioncoefficient that is lower than 10.0 μm/m° C.
 2. The joining deviceaccording to claim 1, wherein the material of the joining device body isa silicon nitride ceramic (Si₃N₄) having a heat expansion coefficient of2.5 μm/m° C.
 3. The joining device according to claim 1, wherein thematerial of the joining device body is an iron nickel alloy having aheat expansion coefficient of 1.7 μm/m° C.
 4. The joining deviceaccording to claim 1, wherein the joining device body is structured forthermally joining the components on the shaft.
 5. The joining deviceaccording to claim 1, wherein the joining device body is structured forpress-fitting the components on the shaft.
 6. The joining deviceaccording to claim 1, wherein the joining device body includes aplurality of openings for receiving the shaft, the plurality of openingsbeing surrounded by the material with the heat expansion coefficientthat is lower than 10.0 μm/m° C.
 7. The joining device according toclaim 1, wherein the joining device body includes transverse wallsarranged axially spaced apart at a distance from one another relative toa shaft axis, and wherein transverse walls have a respective opening forreceiving the shaft and are composed of the material with the heatexpansion coefficient that is lower than 10.0 μm/m° C.
 8. The joiningdevice according to claim 7, wherein the transverse walls are composedof a silicon nitride ceramic (Si₃N₄) having a heat expansion coefficient2.5 μm/m° C.
 9. The joining device according to claim 7, wherein thetransverse walls are composed of an iron nickel alloy having a heatexpansion coefficient of 1.7 μm/m° C.
 10. The joining device accordingto claim 1, wherein the heat expansion coefficient of the material ofthe joining device body is smaller than that of the components and theshaft.
 11. A joining device for joining camshaft components on acamshaft tube, comprising: a joining device body composed of a materialwith a heat expansion coefficient that is lower than 10.0 μm/m° C. 12.The joining device according to claim 11, wherein the material of thejoining device body is a silicon nitride ceramic (Si₃N₄) having a heatexpansion coefficient 2.5 μm/m° C.
 13. The joining device according toclaim 11, wherein the material of the joining device body is an ironnickel alloy having a heat expansion coefficient of 1.7 μm/m° C.
 14. Thejoining device according to claim 11, wherein the joining device bodyincludes transverse walls arranged axially spaced apart at a distancefrom one another relative to a shaft axis, and wherein transverse wallshave a respective opening for receiving the shaft and the transversewalls are composed of the material with the heat expansion coefficientthat is lower than 10.0 μm/m° C.
 15. The joining device according toclaim 14, wherein the transverse walls have an axial extent of 30 mm.16. The joining device according to claim 11, wherein the joining devicebody is structured for thermally joining the camshaft components on thecamshaft tube.
 17. The joining device according to claim 11, wherein thejoining device body is structured for press-fitting the camshaftcomponents on the camshaft tube.
 18. The joining device according toclaim 11, wherein the camshaft components include at least one of adrive element and a cam.
 19. The joining device according to claim 11,the heat expansion coefficient of the material of the joining devicebody is smaller than that of the camshaft components and the camshafttube.
 20. The joining device according to claim 11, wherein the joiningdevice body includes a plurality of openings for receiving the camshafttube, the plurality of openings being surrounded by the material withthe heat expansion coefficient that is lower than 10.0 μm/m° C.